iperf - A TCP, UDP, and SCTP network bandwidth measurement tool
benchmark.js - A benchmarking library that supports high-resolution timers & returns statistically significant results.
netperf - Netperf is a benchmark that can be used to measure the performance of many different types of networking. It provides tests for both unidirectional throughput, and end-to-end latency. - HewlettPack...
PPerf - PowerShell Iperf GUI - A PowerShell script to start iperf and show the output (similar to Jperf).
JPerf - This project gives a better UI and new functionalities to the initial JPerf 1.
NetStress - NetStress is a user-friendly benchmarking tool that is mostly used by networking professionals to measure the network performance of both wired and wireless connections.